The goals of the proposed research are to determine the structural and functional organization of the genes which encode yeast enolases and glyceraldehyde-3-phosphate dehydrogenases. The three glyceraldehyde-3-phosphate dehydrogenase and two enolase genes from yeast have been isolated on bacterial plasmids and their complete nucleotide sequences have been determined. Utilizing this structural information we propose to study their expression and mechanism of selective transcription. It is proposed that coding region deletions within the isolated structural genes be recombined in place of the wild type genes in yeast by transformation. Mutants containing deletions in single enolase and glyceraldehyde-3-phosphate dehydrogenase genes respectively will be crossed and haploids containing deletions in two structural genes will be identified by Southern blotting. Utilizing these mutants the expression of a single wild type gene will be studied to determine the transcriptional activity of each gene repeat. The expression of gene fusions between two enolase or glyceraldehyde-3-phosphate dehydrogenase genes will be investigated to determine the role of 5' and 3' noncoding regions of the genes on transcriptional and translational efficiency. The 5' noncoding sequences of a glyceraldehyde-3-phosphate dehydrogenase gene will be fused to a yeast cytochrome c structural gene and the expression of this hybrid gene will be studied to determine if regulatory sequences reside within the 5' noncoding sequences. Finally we plan to test the effects of crude cellular fractions, on the selective transcription of the isolated yeast glycolytic and ribosomal genes by purified yeast RNA polymerases in vitro.